Term 2: Oblique-slip systems Flashcards
Transpressional and Transtensional deformation
Transpression (TP) causes the long axes of the strain
ellipse to form at a lower angle to the PDZ.
Transtension (TT) – long axes forms at higher angle to the PDZ
both also involve a vertical component of deformation so get complex 3D patterns
Types of deformation in oblique systems
In oblique compressional systems, strain may be homogeneous or partitioned into domains of wrench & pure shear-dominated deformation
Homogenous produces incline folds
Partitioned produces echelon folds
Strike-slip shuffle
TRANSPRESSION
During evolution of a major continental transform, pieces of crust may be sliced off and moved along the margin
They may be accreted elsewhere on the margin after having been displaced for 100-1000s of km
Makes it difficult to reconstruct history in ancient orogenic belts
Strike slip terrane tectonics: Western USA cordillera
Escape tectonics
Continent-continent collision where lithospheric blocks move laterally out of the collision zone
e.g. Himilayan Orogeny
Vertical and horizontal partitioning
TRANSPRESSION
Depending on lithology and temperature (rheology) various types of partitioning may take place vertically through the lithosphere
Here, strain partitioned in upper crust overlying homogeneous transpression in lithosphere
e.g Central California
Transtension
Extension and strike slip at the same time
Transtension in the Northumberland basin
Late Carboniferous strain is highly heterogenous due to kinematic partitioning
2 structurally distinct domains are identified
Wrench dominated domains (WDD) - twisted rocks
Extension dominated domains (EDD) - extension of rocks
WDD structures
Vertical and horizontal shortening
Wrench dominated domains
dextral strike-slip faults are the dominant structures
at both regional and outcrop scale
Styolites, reverse faults, folds
EDD structures
Vertical shortening - Conjugate normal faults